1. Field of the Invention
The present invention relates to a touch sensor drive system, and more particularly, to an apparatus and method for driving a touch sensor that is capable of reducing touch calculation time and power consumption.
2. Discussion of the Related Art
In recent years, a touch sensor (touchscreen, touch panel) enabling information to be input on screens of various display devices by touch has been widely used as an information input device of a computer system. Users can move and select displayed information simply by touching a screen using a finger or stylus, and therefore, people of all ages and both sexes can easily use such a touch sensor.
The touch sensor senses a position at which touch is generated on the screen of a display device and outputs touch information. A computer system analyzes the touch information and executes a command. A flat display device, such as a liquid crystal display device, a plasma display panel and an organic light emitting diode display device, is mainly used as the display device.
Based on sensing principles, the touch sensor is classified as a capacitive type, a photo type, an infrared type, an ultrasonic type or an electromagnetic type touch sensor. The touch sensor may be an on-cell touch sensor which is manufactured in the form of a panel and attached to the top of a display device or an in-cell touch sensor incorporated in a pixel matrix of the display device. A photo touch sensor to sense touch based on photo intensity using a photo transistor and a capacitive touch sensor to recognize touch based on capacitive variation are most commonly used as the touch sensor.
Generally, the touch sensor includes a plurality of first conduction lines to supply drive signals from a touch controller and a plurality of second conduction lines to output readout signals indicating whether touch has been made. The touch controller sequentially senses readout signals output from the second conduction lines, while sequentially driving the first conduction lines, to determine whether touch has been made.
On the other hand, a conventional touch controller calculates readout signals output from the second conduction lines per channel using a touch algorithm, while periodically scanning all of the first conduction lines of the touch sensor per channel irrespective of the number of touch points, to determine whether touch has been made. In the conventional touch sensor, therefore, the entirety of the touch sensor is scanned per channel even when no touch point is generated or only one touch point is generated, and touch algorithm calculation is performed per channel to sense whether touch has been made. As a result, reduction of touch calculation time and power consumption is limited due to unnecessary touch calculation time. As the size of the touch sensor increases, touch calculation time and power consumption also increase.
A host computer analyzes touch information sensed by the touch controller and executes a corresponding command. Also, if touch is not continuously generated on the touch sensor, and therefore, touch information from the touch controller is not input to the host computer within a predetermined time, the host computer switches the touch controller to a power save mode, thereby reducing power consumption.
Even in the power save mode, however, the conventional touch controller calculates readout signals output from readout lines per channel using a touch algorithm, while periodically scanning all of the scan lines of the touch sensor per channel, to determine whether touch has been made. Even in the power save mode, therefore, the conventional touch controller performs touch algorithm calculation per channel, while scanning the entire region of the touch sensor per channel, to sense whether touch has been made. For this reason, reduction of power consumption of the conventional touch controller is limited.